2 December 1941:
TENYO MARU receives the signal "Niitakayama nobore (Climb Mt. Niitaka) 1208" from the Combined Fleet. This signifies that X-Day hostilities will commence on 8 December (Japan time).

3 December 1941:
At 1130 minelayer OKINOSHIMA and TENYO MARU arrive at Jaluit.

6 December 1941:
Jaluit. Embarks troops and departs with OKINOSHIMA and NAGATA MARU.

8 December 1941: Operation "Gi”:
Assigned to the Gilbert Islands Invasion Force that includes minelayers TSUGARU and TOKIWA carrying the 51st Guards Unit escorted by DesDiv 29/Section 1's ASANAGI and YUNAGI. The CHITOSE Naval Air Group provides air cover. At 1300 departs Jaluit.

10 December 1941:
At 0045, TENYO MARU and OKINOSHIMA arrive at Makin and disembark SNLF troops. By 0515, the island is secured. At 0841, auxiliary gunboat NAGATA MARU enters the Makin lagoon and unloads seaplane construction materials. Within two days a flying boat facility is completed.

21 December 1941: The Second Invasion of Wake Island:
The greatly reinforced Attack Force consisting of two fleet carriers, a seaplane tender, six heavy cruisers, two light cruisers and 11 destroyers sorties from Roi in support of the second invasion's troop transports.

23 December 1941:
After a magnificent, but hopeless stand, Wake's grossly outnumbered American garrison is overwhelmed and forced to surrender.

24 December 1941:
TENYO MARU departs Roi for Wake Island.

26 December 1941:
Arrives at Wake island and departs later that day.

29 December 1941:
Arrives back at Roi.

4 January 1942:
At 0600 departs Roi.

7 January 1942: Operation "R" - The Invasions of Rabaul, New Britain and Kavieng, New Ireland:
TENYO MARU is assigned to the main body for the capture of Rabaul. That same day at 0725 arrives at Truk.

13 February 1942:
At 1000 arrives at Jolo and departs later that day at 1600.

20 February 1942:
At 0730 arrives at Kavieng and departs later that day at 1500.

21 February 1942:
At 0600 arrives at Rabaul.

25 February 1942: Operation “SR” – The Invasion of Lae and Salamaua, New Guinea:
Loads troops for landings at Salamaua, New Guinea. The convoy consists of TENYO MARU and transports KONGO and KOKAI MARUs to Lae and YOKOHAMA and CHINA MARUs for Salamaua. Armed merchant cruiser KINRYU MARU is part of the escort providing support.

5 March 1942:
At 1300 departs Rabaul.

8 March 1942:
Arrives at Lae-Salamaua. The invasion force unloads troops and cargo.